1. Field of the Invention
This invention relates generally to the field of self-cleaning nozzles and the like, that are used for providing a directional spray or stream of a pressurized fluid from a conduit. More particularly, it relates to a nozzle that is selectively operable in a first mode to direct a spray or stream of fluid from its outlet, and in a second mode to flush the nozzle with a purging flow of the fluid.
2. Discussion of the Prior Art
Spray nozzles have long been used in the food processing and packaging industry to spray lubricating and cleaning solutions onto conveyers for bottles, cans and other packages. A conveyer lubricating system that uses a spray nozzle is disclosed in U.S. Pat. No. 4,262,776 to Wilson et al. The nozzles in such systems are, however, prone to clogging, due to the nature of the lubricants used in such systems, which typically contain soapy detergents, which create build-ups of deposits The situation is where hard water is used to dilute the lubricant, because of the build-up of mineral deposits, and where the conveyer is run through refrigerated areas, where the lubricant tends to degrade and thicken. Other sources of clogging are particulate or fibrous debris in the system, and microbiological growth in the nozzle.
Typically, conveyer lubricating systems use flow rates through the nozzles of about one to five gallons per hour. Typical nozzle orifice diameters are in the range of about 0.01 to 0.10 inches, operating at pressures ranging from about 10 to 60 psi. Such low flow rates and relatively low pressures exacerbate the problem of nozzle clogging
Consequently, frequent manual cleaning of the spray nozzles is required. This leads to costly down-time for the conveyer, or attempts to clean the nozzles while the conveyer is moving, which present a danger of injury to the workers.
Similar problems are present in irrigation systems that use low flow-rate spray nozzles. Such nozzles frequently become clogged with algae, or with mineral deposits from "white" water.
Ideally, the solution to the clogging problem would be the use of self-cleaning nozzles. Such nozzles are known in the art, as exemplified by U.S. Pat. No. 3,685,735 to Foster. Nozzles of the type disclosed in the Foster patent provide a spraying action in their normal mode of operation. When the line pressure drops below a certain level, however, a spring-biased piston is retracted to open the outlet orifice more widely, thereby allowing a purging flow through the orifice to remove debris therefrom. The need to maintain a relatively high dynamic line pressure to operate this type of nozzle in its normal, spraying mode, however, is contrary to the need for low pressure spraying in conveyer lubricating applications, making this type of nozzle unsuitable for such applications.
There exist nozzles that provide a self-cleaning action in response to a static pressure increase within the nozzle structure resulting from a reduction in flow through the nozzle, as from clogging. See, for example, U.S. Pat. No. 3,203,629 to Goddard; and U.S. Pat. No. 3,430,643 to Heiland. These nozzles do not, however, permit a "purge" mode to be selected by increasing the dynamic ("line") pressure of the flow to the nozzle above a predefined threshold pressure.
There has thus been a long-felt, but as yet unsatisfied need in the food and beverage industry for a spray nozzle that provides a directional spray at low flow rates and low pressures, and that can be selectively operated in a purge mode by exceeding a preselected threshold line pressure to unclog the nozzle.